Shape memory alloy (SMA) actuators are used for a wide range of applications. One typically application for SMA actuators is to perform limited displacements which generate work. In such displacement applications, the SMA actuator is typically in the form of a wire that transforms linear motion into incremental relative motion. When applying a current to the cold (low temperature or martensitic state) shape memory alloy (SMA) wire the temperature rises until the transformation temperature is reached (high temperature or austenite state) and due to a crystalline restructuring of the material, a contraction occurs. With such a contraction, force or torque is thus generated. However, it is to be appreciated that after the contraction, the SMA wire does not reset itself and therefore a counterforce has to bring the SMA wire into its original position.
In the field of drug delivery devices, prior art drug delivery systems which use shape memory alloy actuators are typically reset by having opposed SMA wires. Such a configuration allows higher cycle frequencies. However, such a design is more complex and additional space is required for the second SMA wire.